Automatic transmission and controls

ABSTRACT

Power transmission having torque converter drivingly connected to a planetary gear unit conditionable by selective engagement of friction drive establishing devices to provide for four forward drives and one reverse drive. A converter clutch normally held from engagement by the feed of fluid into the converter through a clutch control chamber can be engaged by converter pressure in response to an upshift signal and subsequent exhaust of fluid from the control chamber to permit mechanical drive of the gear unit. A shift valve forming part of hydraulic controls provides a signal pressure to open a converter feed restrictor valve to permit the converter to be fed with operating oil through a second feed passage. The signal from this valve also activates an accumulator valve system which controls the engagement of the converter clutch so that converter clutch capacity is gradually increased to a maximum. There is a detent valve which provides for 3-2 and 4-3 part throttle downshifts and 4-2, 3-2 and 2-1 full throttle downshifts.

United States Patent 1 1 Chana AUTOMATIC TRANSMISSION AND CONTROLSInventor: Howard E. Chana, 1305 Westwood Dr., Flint, Mich. 48504 Filed:Sept. 3, 1971 Appl. No.: 177,771

Related US. Application Data Division of Ser. No. 59,467, July 30, 1970,Pat. No. 3,638,771.

Primary er-A hur T- MKE9E! Attorney-W. E. Finken, Charles R. White eta].

[4.5] Aug. 14., 1973 [57] ABSTRACT Power transmission having torqueconverter drivingly connected to a planetary gear unit conditionable byselective engagement of friction drive establishing devices to providefor four forward drives and one reverse drive. A converter clutchnormally held from engagement by the feed of fluid into the converterthrough a clutch control chamber can be engaged by converter pressure inresponse to an upshift signal and subsequent exhaust of fluid from thecontrol chamber to permit mechanical drive of the gear unit. A shiftvalve forming part of hydraulic controls provides a signal pressure toopen a converter feed restrictor valve to permit the converter to be fedwith operating oil through a second feed passage. The signal from thisvalve also activates an accumulator valve system'which controls theengagement of the converter clutch so that converter clutch capacity isgradually increased to a maximum. There is a detent valve which providesfor 3-2 and 4-3 part throttle downshifts and 4-2, 3-2 and 2-1 fullthrottle downshifts.

12 Claims, 5 Drawing Figures Patented Aug. 14, 1973 I5 Sheets-Sheet .1.

Patented Aug. 14, 1973 3,752,009

3 Sheets-Sheet :1

CONVERTER OUT RESTRICTOR 6? INVENTOR.

Z50 BY Hall/am 6 621mm DETENT :22s::zR 5594a zmzm ATTORNEY Patented Aug.14, 1973 3,752,009

3 Sheets-s 3 L0 CONTROL VALVE MANUAL VALVE P R N ERNO 3 VALV OLENOI Lg}?ward am ATTQRNEY .MODULATOR VALVE MODULATOR T VALVE AUTOMATICTRANSMISSION AND CONTROLS This application is a Division of myco-pending application entitled Automatic Transmission and Controls,"Ser. No. 59,467, filed July 30, 1970, now U.S. Pat. No. 3,638,771.

This invention relates to automatic transmissions and controls whichprovide for automatic all hydraulic, split torque or all mechanicaldrive. More particularly, this invention relates to advanced hydrauliccontrols for the transmission gearing and for the control of a frontclutch using converter pressure.

Automatic transmissions with a large number of gear ratios have employeda front clutch for mechanical drive of planetary gearing to produce anoverdrive ratio and to cooperate with torque converter drive of thegearing to produce split torque drives. The gearing, clutches and brakesand hydraulic controls comprising such transmissions have generally beenhighly complex, expensive and therefor impractical for mass productionand have not had wide-spread usage. In many cases a special planetarygear unit had to be employed for an overdrive ratio greatly adding tothe transmission weight and complexity. This invention provides for newand improved torque converter, converter clutch, planetary gear unit andcontrols to produce all hydraulic low and intermediate-drives, a splittorque 1:] drive and an all mechanical overdrive. This inventionutilizes only simple planetary gearsets, a minimum number of frictiondrive establishing devices and uncomplicated controls providing a highlysuitable transmission for quantity production. The converter clutch isengaged by the force of converter pressure to provide for mechanicaldrive into the planetary gear unit to improve efficiency of transmissionoperation for vehicle cruis ing. The controls include 12, 2-3 and 34shift valves which respond to torque demand and vehicle speed signals byupshifting and downshifting for automatic operation of the transmission.Operating oil is fed to the converter from the 2-3 shift valve whendownshifted through a control chamber for the front clutch to effectFIG. 3 is a diagram showing how FIGS. 4a and 4b are to be placed toillustrate a complete transmission control.

FIG. 4a is a diagrammatic view of a first part of the transmissioncontrol of this invention.

FIG. 4b is a diagrammatic view of a second part of the transmissioncontrol of this invention.

As shown in FIG. 1 this transmission has an input 10 which is drivinglyconnected to the front cover of a housing 12 of a hydrodynamic torqueconverter 14. The torque converter has a bladed pump 16 operativelyconnected to housing 12 and has a bladed turbine 18 and stator 20. Thestator is connected through a oneway brake 22 to a ground sleeve 24. Theturbine 18 is drivingly connected to the flange of a hub 26 which issplined to a sleeve shaft 28. Sleeve shaft 23 extends rearwardly in thetransmission and is splined to the inner hub of an annular drum 30. Thisdrum houses the friction plates of a forward drive clutch 32 havingdrive plates splined to the interior wall of the drum and having drivenplates, disposed between the drive plates, splined to the outerperiphery of annular plate support hub 34. The support hub is splined toan intermediate sleeve shaft 36 which drives a first planetary gearset38.

An annular piston 40 is housed in drum 30 and cooperates therewith toform clutch apply chambers 41 and 42 connected by restricted passage 43.When working fluid under pressure is supplied to chambers 41 and 42through forward clutch line 46, the piston will move axially to effectengagement of forward clutch 32. By virtue of the restricted passage 43,chamber 41 gradually fills with this fluid to increase clutch capacity.This dual capacity clutch construction provides for softer and bettertimed shifts particularly a 4-3 downshift when the chambers areexhausted. Spring 44 is a return spring supported in drum 30 forengaging and moving the piston from engagement with clutch 32 when thepressure fluid in the apply chambers is exhausted.

release of the front clutch so that first and second range drives areall converter drives. When upshifted, the 23 shift valve provides asignal that opens a restrictor valve so that fluid is fed to theconverter through a second feed passage. An accumulator valvesystemcontrols the engagement of the converter clutch to provideimproved shifting into direct drive. After the 2-3 shift valve signalsan upshift, the control fluid from the clutch chamber is graduallyexhausted so that the clutch capacity gradually increases to a maximumwhen the accumulator has obtained its maximum capacity. The controlsinclude a detent valve which modifies theshift schedule of thetransmission and provides for 3-2 and 4-3 part-throttle downshifts and42, 3-2 and 2-1 wide-open-throttle downshifts. Low, intermediate andreverse drives may be manually selected by moving the manual valve topredetermined positions to set the automatic controls for theserespective operations.

These and other features, advantages and objects of the invention willbecome more apparent from the following detailed description anddrawings in which:

FIG. 1 is a longitudinal sectional view of a portion of thetransmission.

FIG. 2 is a chart which illustrates operation of the converter clutch ofthis transmission.

Theintermediate shaft 36 is splined to the sun gear 48 of the firstplanetary gearset 38. This gearset has elongated planet gears 49 whichmesh with the sun gear 48 and also with a ring gear 50 which has aninner hub portion splined to the end of a drive shaft 51. This driveshaft extends longitudinally in the transmission and has its forward endsplined to a front annular hub 52. This hub has an annular shoulder 53that slidably supports a disk-like plate 54 having an outer annularfriction member that is engageable and disengageable with a frictionsurface on the inside of the front cover of the converter housing 12 toprovide a front clutch 55. The plate 54 carries a series of rearwardlyprojecting fingers 56 that extend into openings formed in a radialflange 57 of the hub 52 to drivingly connect the friction plate and thehub and the drive shaft 51. Tickle spring 58 trapped between the flange57 and the friction plate 54 urges the friction plate forwardly so thatthe clutch 55 has a positive engagement bias at all times. The frictionplate 54 and the front cover of the converter housing form a chamber 59which is connected by a passage 60 to a converter clutch line 611.Operating fluid when supplied to the converter through line 61, passage60 and chamber 59 effects disengagement of clutch 55 while feeding theconverter.

The planetary gearset 38 has a carrier 62 which fixedly supports pivotpins 63 on which planet gears 49 are rotatably mounted. The planetarycarrier is rigidly secured to the interior of an output shell 65 whichis splined to a rearwardlyextending output shaft 64. Also, thisplanetary gearset has a second ring gear 66 meshing with planet gears 49which has a forwardly extending portion that surrounds a secondplanetary gearset 68 disposed adjacent to the planetary gearset38.

Planetary gearset 68 has a sun gear 70 which meshes with the planetgears 72 that in turn mesh with the ring gear 74. Ring gear 74 extendsrearwardly and is connected to the carrier 62 of the first gearset whilethe carrier 76 of planet gears 72 of the second gearset is rigidlysecured to the interior of the extension of ring gear 66.

A multi-plate low and reverse friction brake 78, disposed between ringgear 66 and the interior of transmission housing 80, is engageable by ahydraulically operated piston 82 to connect the ring gear to the housingto establish low and reverse drive ratios as will be further explainedbelow. This piston is movably mounted in the rear of the transmissionhousing and cooperates therewith to form separate pressure chambers 84and 86 connected to low and reverse line 85 and reverse line 87respectively of the transmission controls. For manual low speed drives,chamber 84 is supplied with pressurized working fluid to effect themovement of piston 82 and the engagement of brake 78. For reverse,higher reaction torques are needed and the torque capacity of brake 78is increased by charging both chambers with working fluid. Returnsprings 88 secured to housing 80 move the piston to the off positionwhen the apply chambers are exhausted.

Disposed adjacent to multi-plate brake 78 is a oneway brake 90operatively connected to the outer periphery of ring gear 66 and theinterior of the transmission housing. This brake automatically engagesto prevent the reverse rotation of the ring gear 66 and the carrier 76and automatically disengages to allow these elements to rotateforwardly.

The sun gear 70 of the second planetary gearset has a forwardlyextending sleeve portion concentric with driven plates splined to theinterior of drum 94 and drive plates interleaved with the driven platesand splined to an annular shoulder extending forwardly from drum 30. Theengagement of clutch 102 connects drums 94 and 30 together. Returnsprings 104 secured to drum 94 engage the piston 97 to move it to an offposition when chambers 98 and 99 are exhausted. Conventional ball dumpvalves such as valve 105 are employed in this transmission. This valveopens to exhaust chamber 98 when the drum 94 is rotating to preventresidual centrifugal oil from effecting movement of piston 97 andengagement of clutch 102. There is an annular brake band 103 which isoperated by a servo mechanism for selectively engaging drum 94 to holdit from rotation when establishing predetermined ratios.

Mounted on a forwardly extending collar portion of drum 94 is the innerrace of a one-way clutch 106. There is also a multi-plate intermediatebrake 108 having a first series of plates splined to the outer race ofthis one-way device and a second series of plates splined to theinterior of housing 80. Piston 110 slidably mounted on an interiorshoulder of transmission housing 80 engages the brake 108 when thepressure chamber 112 formed by this piston and the housing is chargedwith apply pressure through intermediate clutch line 1 14. Suitablereturn spring means supported on the transmission case are employed tomove piston 110 to an inactive or off position when the associated applychamber is exhausted.

instead of being supplied with working fluid through passage 60 theconverter 14 may also be supplied with working fluid through feed line118 and passage 120. in both cases converter discharge is throughpassage 122 into converter out passage 124.

With the invention as shown and described a plurality of forward driveratios, a neutral and a reverse drive ratio can be readily obtained. Theschedule of engagement of the clutches and brakes to obtain these ratiosis set forth in the following chart:

Friction elements Example 102 32 108 78 103 106 90 Converter ratio Neutr 2. 87/1 I 1.04/1 :3 1/1 6A (Optlon). 1/1 315 (Option). 1/1 w t 66/1marsh-45a i317 Reverse 1. 94/1 sleeve shaft 36 and this sleeve portionis connected to a sheet metal drum 92 that extends forwardly around drum30. As shown, drum 92 has extending tabs or projections which fit inspecial openings formed in an annular flange portion of a drum 94 whichis rotatably mounted on an inner-extending shoulder portion 95 of thetransmission housing. The drum houses a piston 97 which forms pressurechambers 98 and 99 within the drum 94 connected by passages 100 and 101to reverse passage 109 and reverse clutch line 107 respectively. Applyoil when fed by the controls to chamber 99 or both chambers 98 and 99,causes the piston to engage a multi-plate reverse drive clutch 102. Thisclutch has When the transmission is set for automatic drive, first,second, third and fourth speed ratios are automatically selected inaccordance with torque demand and vehicle speed signals. When torquerequirements are high as when initially moving the vehicle, forwardclutch 32 is applied' Turbine torque is transmitted by clutch 32 throughsleeve shaft 36 to the sun gear 48 of the planetary gearset 38. Ringgear 66 will be held by the one-way brake and the carrier 62 will bedriven forwardly at low speed in the largest reduction ratios such aslisted in the schedule. The one-way clutch 106 locks but this does notaffect the drive since brake 108 is released at this time.

As vehicle speed increases and torque demand decreases the transmissionupshifts into second gear. in this gear the intermediate brake 108 isapplied in addition to forward clutch 32 as shown in the schedule. Underthese conditions the outer race of one-way clutch 106 is grounded andthis one-way device locks to hold sun gear 70 for reaction. With ringgear 74 rotating forwardly and with sun gear 70 held, the planet gears72 will be driven forwardly. The output speed of ring gear 74 andconnected output shaft 64 increase as the planet gears walk on thestationary sun gear 70 to produce an intermediate speed ratio. Duringthis drive the one-way brake 90 overruns. For a preferred split torquedirect drive indicated as drive 3, the front clutch 55and forward clutch32 are applied. Under these conditions sun gear 48 will be driven by theconverter and ring gear 50 will be driven mechanically to produce aratio of 1:1. This drive will be two-thirds mechanical and one-thirdhydraulic. The intermediate brake 108 is on but has no effect on thisdrive since the one-way clutch 106 overruns.

For a torque converter direct or third range drive, clutches 102 and 32are applied as indicated by optional drive 3A. Under these conditionsthe sun gears 70 and 48 are connected and the planetary gearset islocked up for rotation as a unit in a ratio of 1:1. intermediate brake108 is on but has no effect on this operation since the one-way clutch106 overruns.

if an all mechanical direct drive is desired the front clutch 55 isadditionally engaged as indicated in optional drive3B. With the gearsetlocked and driven mechanically through the clutch 55 there is noconverter slippage and operating efficiency is improved.

For overdrive, front clutch 55 and brake band 103 are engaged. With sungear 70 held for reaction and ring gear 50 mechanically drivenforwardly, an all mechanical overdrive is produced with the carrier 62and output shaft rotating faster than input 10.

For low hold, forward clutch 32 and brake 78 are applied. With sun gear48 driven forwardly by the converter and ring gear 66 held for reactionthe carrier 62 and connected output shaft will be driven forwardly atthe low speed ratio. Since brake 78 is engaged the ring gear 66 is heldfrom rotation so that it cannot overrun the one-way brake 90 to preventfree-wheeling under coast conditions for engine braking. As shown in theschedule, one-way brake 90 is onto assist in holding the ring gear fromreverse rotation.

For intermediate hold, forward clutch 32 is engaged to transmitconverter torque to sun gear 48 and brake band 103 is engaged with drum94 to hold sun gear 70 for reaction. Under these conditions the twocarriers 62 and 76 compound so that forward rotation of sun gear 48results in forward-medium speed drive of the carrier 62 and theconnected output shaft 64. The application of brake band 103 preventsfreewheeling of the oneway device 106 under predetermined coastconditions.

For reverse, brake 78 and clutch 102 are engaged. Under these conditionswith sun gear 70 driven forwardly and with carrier 76 held for reaction,the ring gear 74 and the connected output shaft are driven in a reversedirection at a reduced speed.

In neutral all clutches and brakes are released and the gearset isstationary for any input speed.

In the preferred embodiment sun gear 70 has 38 teeth, ring gear 74 has74 teeth, sun gear 48 has 46 teeth and ring gears 66 and 50 have 86teeth each to produce the example gear ratios listed above. Otherbeneficial ratios can be readily produced by appropriately changing theteeth numbers of the gearing components.

The hydraulic controls of this invention include an internal-externalgear type pump disposed immediately behind the torque converter pumpwithin a pump housing 134 disposed in the transmission housing 80. Theexternal gear of the pump is keyed to a sleeve 136 of the converter pump16 so that the pump 130 pumps transmission oil whenever the engine isoperating.

As shown schematically in FIGS. 4a and 4b the pump has an intakeconnected to suction line 138 which is connected to an oil strainerassembly and sump 140. Oil is delivered by the pump into main line 142.Oil pressure in the control system is controlled by a pressure regulatorvalve 144 which is spring balanced to regulate line pressure at apredetermined value. The regulator valve has a main valve element 146, amodulator trim and reverse boost element 148 forming a boost chamber 149connected to reverse line 07, and a pressure boost plug 150. Minimumregulated line pressure is controlled by a centrally disposed spring 152which is seated in the bore of valve 144 and which has a free endengaging the end of the main valve element 146. Main line pressure isfed to a chamber 153 located in one end of the regulator valve to exerta force on the main valve element 146 which opposes the force exerted bythe spring 152. As the pressure builds up in the chamber 153, the mainvalve element 146 moves down against the spring 152 to reduce linepressure by exhausting pressure fluid to suction line 155 connected tothe sump 140. The movement of this valve element opens converter feedport and connected converter feed line 110 to a main pressure port 160connected to the main line 142. The converter feed line 110 is connectedto a converter blow-off valve 161 and also into the passage 120 througha converter feed restrictor valve 162. If main line pressure continuesto increase in chamber 153, the valve element will open pressure port160 to an exhaust port 164 connected to the suction line leading intosump 140. if the pressure in the main line drops, the spring 152 willmove the main valve element 146 into a position blocking main linepressure port from the exhaust port 164 to effect a main line pressurerise. To provide for increased regulated pressure, the modulator trimand reverse boost valve element 146 can be moved to exert a force on themain regulator valve tending to close main line pressure port 160 fromexhaust port 164 regardless of line pressure. This occurs when there isa supply of a reverse pressure through reverse line 87 to act on thedifferential area of the lands of the boost element 144. Also, pressurefrom a modulator trim valve which will be later described, can besupplied to a pressure chamber 165 formed between boost element 148 andplug 150. When this chamber is charged with pressure oil, an additionalforce is exerted on the main valve element 146 to increase main linepressure. The regulated pressure can also be increased by supply of aboost pressure to chamber behind boost plug 150 through boost line 172.The force exerted by this boost pressure urges the plug 150 and valveelement 146 against the end of the main regulator valve element 146moving it toward the illustrated position. In this position the suctionline 155 is blocked from pressure port 160 and the main line pressure isthereby increased.

Regulated main line pressure is routed through line 142 into a port 176of a manual valve 178 which has a valve element 180 axially shiftable bya manual selector lever or other selector mechanism to the illustratedpositions L L,, D, N, R, P which correspond to low, intermediate, drive,neutral, reverse and park, respectively.

In the L or low range position the manual valve element 180 connectsmain line pressure to a low control line 182, a drive line 184 and anintermediate line 186. In the L or intermediate position of the manualvalve element, main line pressure is connected to the drive andintermediate lines. The low pressure line is exhausted through passage187 in the manual valve element and exhaust ports 188. In the driveposition D the manual valve element is shifted to a position in whichmain line pressure is connected to a reverse-neutraldrive or RND line192 and to drive line 184. The intermediate and low lines are exhaustedthrough passage 187 and exhausts 188. In the neutral position the mainline pressure port 176 is connected to the RND line 192 and all of theother lines connected into the manual valve are exhausted. in reverseposition the main line pressure is connected to a reverse port 1 94,reverse line 87 while the RND line 192 and the other lines are opened tothe exhausts 188. In park, the main line pressure port 176 is blocked bythe shifted manual valve element and all other lines are exhausted.

Vehicle speed signal for automatic shifting is supplied by a suitabletransmission governor 198 such as the governor shown in US. Pat. No.3,541,887 issued Nov. 24, I970 to Henri J. Van Lent et al., which isdriven by the transmission output shaft 64. The governor is fed withdrive oil from the manual valve through line 184 and provides a governorpressure into governor line 200.

To provide a variable engine torque signal the controls include amodulator valve 204 in which a modulator valve element 206 operating asa simple regulating valve converts modulator force into a hydraulicmodulator pressure. This valve has inlet port 208 connected to main line142, a modulator outlet port connected to modulator line 210 and has anexhaust 211. An engine torque signal is exerted on one end of themodulator valve element 206 by a suitable vacuum modulator such as thatdisclosed in the above-identified patent to Henri J. Van Lent et al.

Modulator pressure is fed into end chamber 212 of the modulator valvethrough a suitable passage 213 in the modulator valve element to exert aforce opposing that of the vacuum modulator. The modulator force andthus modulator pressure increase with increased engine manifoldpressure. Modulator pressure is supplied through the modulator line 210to an end chamber 215 in a modulator trim valve 214 and to a chamber 217in a 3-4 shift valve 216.

The modulator trim valve produces a pressure fed to a modulator trimline 218 which is directly proportional to modulator pressure andinversely proportional to governor pressure. This valve has an inletport connected to main line 142 and a shiftable valve element 220.Governor pressure is fed by governor line 200 to a chamber 222 at oneend of the valve element which opposes the force of modulator pressurein chamber 215 effective at the other end of the valve. When modulatorpressure is sufficiently high, valve 220 moves to open the inlet or lineport to the modulator trim line 218.

Modulator trim pressure is fed by line 218 to the pressure chamber 165between boost plug and modulator trim and reverse boost valve element148 in the pressure regulator valve to urge valve element 148 to theright against the regulating valve element to effect an increase in linepressure. Also the modulator trim line is connected to an inlet port 225of a detent valve 226.

The detent valve controls or modifies the shift schedule of thetransmission in accordance with engine torque as reflected by throttlecontrol position. With this valve, 3-2 part throttle downshifts, 4-3part throttle downshifts and wide-open throttle 4-2, 3-2 and 2-1downshifts are obtained to improve vehicle performance. The detent valvehas a valve element 228 which is operatively connected to the throttlelinkage, not shown, and is shiftable between the predetermined positionsshown as 0, 3-2, D 'and D in accordance with throttle opening. Axialmovement of the detent valve element 228 in response to the opening ofthe throttle is opposed by coil spring 230 disposed in a spring pocket232 having exhaust 233 at one end of the valve element. This movement isalso opposed by an outer spring 234 trapped between a spring supportsecured to the valve element and a spring seat 238 fixed to the valvehousing. There is an inner coil spring 240 disposed between the outerfixed support 236 and an inner support or washer 242 normally seatedagainst a shoulder on the valve element. After predetermined movement ofthe valve element by the throttle control, washer 242 contacts springseat 238 and spring 240 adds to the force opposing valve movement by thethrottle pedal. As the valve element 228 is moved from the D, to the Dposition spring 240 establishes a detent feel position to inform theoperator that the transmission will be conditioned for wide-openthrottle downshifts on further opening of the throttle.

The detent valve also has: (I) a port connected to a detent-2 line 246leading to the modulator trim valve 214 and into a l-2 shift valve and a2-3 shift valve later described, (2) a detent-1 port connected to adetent-1 line250 leading into the 3-4 shift valve 216, (3) an inlet port252 connected by line 276 to the detent pressure regulator valve 254,(4) an outlet port 256 connected to the modulator shift valve line 258,(5) part throttle port 260 connected to a 3-2 part throttle line 262 and(6) an exhaust 264.

1n the 3-2 part throttle downshift position the 3-2 part throttle port260 is connected to the modulator trim inlet port 225. When the valveelement is moved further down to the D position, the D port is connectedto the detent regulator port 252 and the 3-2 part throttle port remainsconnected to the modulator trim inlet port 225. As the valve element 228moves to the D or wide-open throttle position the 3-2 part throttle port260 remains connected to the modulator trim port but the modulator shiftvalve port 256 becomes connected to the detent regulator port. The Dport, which previously was exhausted is also connected to the detentregulator port in this wide-open throttle position of the detent valveelement. There is a detent ball check valve 268 disposed between themodulator trim line 218 and detent-2 line 246 which blocks flow frommodulator trim line 218 to the detent-2 line; as indicated by the arrow,this valve allows flow from line 246 to line 218. This valve insuresthat in the Q position of the detent valve element, modulator trimpressure can be greater than detent regulated pressure but cannot beless than this pressure.

The detent regulator valve 254 provides a regulated pressure for thedetent valve. This valve has a valve element 270 shiftable in a bore inthe valve housing. This valve has an inlet port 272 connected to mainline 142, a detent regulator port 274 connected to the detent regulatorline 276 and has an exhaust 278. There is an end chamber 280 which isconnected to the detent regulator line 276 and oil from that line is fedinto this chamber through a suitable flow control restriction. The forceexerted by detent regulator pressure on the valve element is opposed byspring 284 disposed in a spring pocket at the other end of the valve.

As shown in FIG. 4b, the controls include a low control valve 288 whichis governor pressure controlled and which limits the speed at which amanual low gear engagement can be made. Once this valve triggers manuallow engagement, the transmission will remain in first gear for as longas the pressure port for low control line 182 in the manual valve ispressurized. The valve 288 has a valve element290 biased in onedirection by a spring 292 disposed in an end chamber 294 against theforce of governor pressure fed by governor line 200 to an end chamber296 in the valve. This valve includes an inlet port 298 connected to thelow range control line 182. Also' low control valve 288 has a manual lowport 300 connected to a manual low line 302 that is connected to port304 of l-2 shift valve 306. Also the manual low line 302 is connected tothe chamber 294 to supply this chamber with pressure when the manualvalve is in the L position. Thus, in manual low a fluid pressure fed tochamber 294 exerts a force on the valve element 290 additive to theforce of spring 292.

The manual low control valve 288 is positioned to exhaust the manual lowline 302 when the manual valve is placed in the manual low position andwhen the vehicle speed is more than a predetermined speed. At.

speeds below this, low range oil is fed by the low control valve intothe manual low line 302. This pressure oil is fed into a chamber 308 inthe 1-2 shift valve between a l-2 shift valve element 310 and a shiftcontrol valve element 312. This pressure moves the 1-2 shift valveelement 310 to the downshifted position to exhaust chamber 112 of theintermediate brake 108 as will be further explained below. The pressurein chamber 308 also moves the l-2 shift control valve element 312 to theupshifted position which sends apply oil to the low and reverse chamber84. Once the manual low control valve element 290 is in the downshiftedposition, the spring 292 plus low apply oil acting on the valve elementwill maintain the valve element in this position. Thus with thetransmission in manual low, the transmission cannot upshift regardlessof vehicle or engine speed once low gear has been engaged.

The l-2 shift valve 306 controls the supply of drive line oil to theservo motor for the intermediate brake to cause the transmission toshift between low and second. This valve is controlled by governorpressure acting on shift valve element 310 and modulator shift valvepressure and spring force acting on shift control valve element 312. Thespring force on this latter valve element is provided by a spring 318located in a pressure chamber 320 which engages the shift control valveelement and determines the minimum shift speeds.

The hydraulic pressures which control the forces on this valve aremodulator shift valve pressure fed to port 319 and to pressure chamber320 by modulator shift valve line 258 and detent-2 pressure fed into theshift valve through spaced ports 322 and 324. The end area of the righthand spool or land controls the part throttle upshift schedule; thesecond or next spool has an area that controls the wide open throttle2-1 downshift point. The areaof the third land c controls the wideopenthrottle l-2 upshift. The shift control valve element 312 also supplieshydraulic pressure to the chamber 84 of the low and reverse brake 78through port 326 and the line 85 leading to the chamber 84 when thetransmission is conditioned for manual, low or reverse. This shiftcontrol valve has reverse port 328 connected to reverse line 87 leadinginto chamber 86 of low and reverse brake 78 and leading into chambers 98and 99 of reverse clutch 102. When shift control valve 312 is upshifted,U-shaped passage 330 connects detent-2 port and detent-2 line 246 tochamber 320 to pressurize chamber 320 to provide for wide-open throttle2-l downshifts in response to movement of the detent valve element 228to the Q position.

The shift valve element 310 has two lands a and 11; land a is acted onby governor pressure fed to an end pressure chamber 337 through line200. The differential area between the two spools gives the valvehysteresis which is an additional force to the right supplied bypressure from drive line 184 when the valve moves to the upshiftedposition. Thus, this shift valve is controlled by the force of governorpressure plus drive pressure acting on the hysteresis area lands a and bwhen valve element 310 is in the upshifted position. When the shiftvalve is in the downshifted position, the 1-2 clutch line 114 connectedto port 338 in the 1-2 shift valve is exhausted by an exhaust port 340having a flow control restriction. As the shift valve moves to theupshifted position, drive pressure through drive line port 344 isconnected to the 1-2 clutch line 114 and is fed by this line directly tothe apply chamber 345 of a servo 346 which operates brake band 103. Theservo has a release chamber 348 connected to a servo control line 352.This control line can be connected to the RND pressure by a 2-3 shiftvalve 354 when downshifted so that the servo cannot apply brake band103. The l-2 clutch pressure supplied through shift valve element 310toclutch line 114 is transmitted through a 1-2 upshift restriction 356,the parallel shift check valve 358 being closed to a l-2 accumulator 360and to intermediate clutch apply chamber 112. The accumulator 360, 1-2orifice 356 and apply chamber 112 are combined to give a smooth shifttransition from first to second. A 2-l shift check valve 364 andrestriction 366 cooperates with the l-2 shift check valve 358,restriction 356 and the exhaust port 340 of the l-2 shift valve .toprovide control of 2-1 downshifts.

The 2-3 shift valve'354 controls shifts between second and third. Thisvalve has a control valve element 370 and a shift valve element 372. Thecontrol valve element transmits the force of modulator shift pressureand the force exerted by a spring 374, disposed in a spring pocketprovided by pressure chamber 376, to the shift valve element 372.Modulator shift valve pressure supplied through line 258 is fed to port378 controlled by the end land a of the control valve element 370. Inthe downshifted position, this valve element permits modulator shiftvalve pressure to be fed to the chamber 376 for part throttleupshifting. The force exerred by modulator shift valve pressure on theshift control valve element 370 is relayed to shift valve element 372.

The 3-2 part throttle line 262 is connected to an inlet port 380 betweenthe first and second lands a and b of valve element 370 having an areadifferential so that 3-2 part throttle pressure urges the shift controlvalve to the downshift position. Detent-Z pressure from the detent valvethrough line 246 is fed to a port 382 between the second and third landsb and c to act on the area differential of these lands to urge thecontrol valve element 370 and the shift valve element 372 to adownshifted position. U-shaped passage 384 connecting port 386 withchamber 376 transmits detent-2 pressure from line 246 into chamber 376when the shift control valve is upshifted. The right side area of theland a controls the part throttle 2-3 ups-' 'ift schedule up to the 3-2position of the detent valve. "After the 3-2 position of the detentvalve, the part throttle upshift schedule becomes controlled by the areaof land b. The difference in area between mentioned lands a and bcontrols the 3-2 part throttle downshifts. The area of land controls thethrough D detent upshifts and downshifts.

The shift valve element 372 has governor pressure from line 200 fed intoan end chamber 388 that urges shift valve element 372 to an upshiftposition. There is a spring 390 disposed in a central chamber 394 actingon an end of the shift valve element 372 opposing the force of governorpressure. The sum of springs 390 and 374 determines the minimum shiftspeeds.

Intermediate pressure from the manual valve 178 supplied to intermediateline 186 is ported to chamber 394 to move the shift valve to thedownshifted position whenever intermediate line 186 is pressurized.

When the shift valve element 372 is downshifted, a RND port 392connected to the RND line 192 is connected to a servo port 395 connectedto servo control line 352 to pressurize the control chamber 348 of theservo 346.

Converter charge pressure from the pressure regulator valve is fed byline 118 into a port 396 of the 2-3 shift valve. This port is connectedto a 2-3 accumulator port 398 for a 2-3 accumulator line 400 when the2-3 shift valve is downshifted. In this valve position a third signalport 402 connected to third range signal line 404 is exhausted throughexhaust 401. When the 2-3 shift valve element 372 moves to the upshiftedposition, the

servo port 395 is connected to a forward clutch port 407 connected toforward clutch line 46 which is pressurized with drive oil from the 3-4shift valve 216 provided the 3-4 shift valve is in the downshiftedposition. Under these conditions the servo cannot effect the engagementof brake band 103. The 2-3 accumulator port 398 is exhausted and thethird signal port 402 which was exhausted becomes pressurized with driveoil. This drive oil also acts on a differential area of the shift valvegiving the shift valve hysteresis control. Pressurizing the third signalport 402 and exhausting the 2-3 accumulator ports 398 activates a 2-3accumulator control valve 406 resulting in a 2-3 shift.

The 2-3 accumulator control valve 406 is provided to control the frontclutch 55 so that it engages properly during a 2-3 shift. This clutch isapplied when chamber 59 is exhausted and converter pressure acting onplate 54 moves it forwardly to-effect the engagement of clutch 55.

The 2-3 accumulator control valve includes a regulator valve 408 whichis urged in one direction by a spring 410 disposed in a pocket formed bypressure chamber 412 located at one end of the valve. Converter feedpressure from line 118 is ported into this chamber. This pressure isalso fed into chamber 413 through port 409 that is controlled by thefirst land of regulator valve 408. A suitable passage through this landconnects chamber 413 with a control chamber 415. converter clutch port416 is connected to converter clutch line 61 through a branch line 418.As shown branch line 418 has a restriction 420 and a check valve 422 inseries and connects into the 2-3 accumulator line 400. This latter lineis connected to the 2-3 accumulator valve by port 426.

To provide an upshift force on the regulator valve 403 the 2-3accumulator has a boost valve 428 which is disposed in a support locatedwithin the valve body. The boost valve is seated on the end of coilspring 430 which extends from a pocket formed in an accumulator piston432 movably mounted in the valve body. The accumulator piston is urgedtoward the boost valve or the upshift position by a spring 434. Driveline pressure from line 184 is fed into the chamber 436 to provide adownshift bias on the accumulator piston.

The accumulator piston is so designed that when it is moved to the fullleft position, it fully compresses the spring 430 and forces the boostvalve and regulator valve to the full left position. When drive linepressure has forced the accumulator piston to the right, which is thedownshift position, the spring 434 will be fully compressed. The 2-3accumulator line 400, port 426, the converter clutch branch line 418 andconverter clutch line 61 are pressurized with converter charge pressurealso fed to the 2-3 shift valve through line 118. The 2-3 accumulatorline and the converter branch line 418 are also connected through the3-2 shift check valve 422. The converter clutch circuit 61 is thereforepressurized with converter pressure releasing the converter clutch. Whena 2-3 shift is signaled by the 2-3 shift valve 354, the 2-3 accumulatorline 400 is exhausted through exhaust 401 in the 2-3 shift valve; the3-2 shift check valve 422 seals allowing the 2-3 accumulator valve toregulate converter pressure.

The 2-3 accumulator valve has a pressure chamber 438 connected by athird signal port to the third signal line 404 through check valve 442and restriction 446. When chamber 438 is fed with third signal pressureequalizing pressure forces on the accumulator piston 432, the spring 434pushes the accumulator piston to the left-hand position. The springs 434and 430 must be selected so that the accumulator piston, acting throughthe boost valve can push the regulator valve'408 to the far left-handposition so that the 2-3 accumulator port 426 is open to exhaust theconverter clutch circuit 61 completely so that the full capacity of theconverter dutch can ultimately be attained. FIG. 2 illustrates theclutch apply sequence as controlled by the 2-3 accumulator valve.

This graph shows the clutch 55 disengaged by converter pressure P beingfed into chamber 59 through line 61 and passage 60 until the 2-3 shiftvalve signals an upshift and clutch engagement. This upshift and initialengagement of the clutch is illustrated at point a on the dashed lineconverter clutch pressure curve, P which represents the pressure inclutch cavity 59. This initial engagement occurs at point 1 on the timescale.

The third signal line 404 is pressurized with drive line oil and theaccumulator valve chamber 438 fills with oil flowing through flowcontrol restriction 446', the chamber expands while the converter feedrestrictor valve 162 opens the supply of oil to the converter throughconverter feed line 118 as the restrictor valve element 460 is moved tothe left against spring 462. At point b on the converter clutch curve Poccurring at point 2 on the time scale clutch engagement has beencompleted. The accumulator piston has moved the regulator valve to,a farleft position to fully open the converter clutch line 61 to exhaustthrough line 480 providing for the full torque transmitting capacity,1?, P of clutch 55. As illustrated by the slope at of pressure curve Pin FIG. 2, the converter clutch pressure in chamber 59 progressivelydecays after initial engagement at point a to point b. After fullengagement the pressure in chamber 59 drops to zero pressure.

It will be appreciated that the accumulator system controls the clutchapply in terms of drive line pressure which is sensitive toengine'torque and vehicle speed as well as being sensitive to the twocalibration springs 430 and 434. This system is not sensitive toconverter pressure which is not easy to control in a transmission. inthis control system the clutch is fully released prior to point 1 on thetime scale and engaged with full capacity after point 2 on the timescale. The engagement time is established by the restriction 446in thethird signal line404, the accumulator valve oil volume, and springs 430and 434. This slope of the converter clutch pressure is controlled bythe rate of spring 438. During downshifts, the accumulator valve systemis bypassed by the shift check valve 422 and restriction 420.

The 3-4 shift or forward clutch control valve 216 consists of threevalves formed by control valve elements 470 and 472 and a shift valveelement 474. The control valve element 472 has end chamber 475 connectedto converter feed line 1 118 so that converter feed pressure operates onthe large area of the land of control valve element 472. This pressureis connected to a chamber 478 on the left side of this spool by a flowcontrol passage 479 in the land. A spring 477 in this chamber urges thevalve element 479 to the right away from valve element 470. Chamber 478is connected to an exhaust 480 through a line controlled by a solenoidoperated valve 484 that is controlled by electric switch 485. When theswitch is open the solenoid is deenergized and the exhaust 480 is sealedallowing a pressure buildup in chamber 478 moving valve element 472 tothe right in a position so that the transmission can shift into fourthrange if modulator pressure is less than a set minimum. When the switch485 is closed the solenoid is energized and the chamber 478 is exhaustedthrough the open exhaust 480. With exhaust 480 open, chamber 478 isevacuated and the valve element 472 will be moved to the left bypressure in chamber 475 pushing 3-4 shift control valve 470 to its fullleft position compressing coil spring 481. Thus the solenoid, whenenergized, deactivates the 3-4 valve system so that shifts to fourthcannot be made and when deenergized makes the selection of the fourthoperating gear possible.

The second control valve 470 is a simple two position valve; however, itcan only function when the first control valve element 472 is in theright-hand position with chamber 478 pressurized. Valve 470 is urged tothe right by spring 481 and to the left by a torque-demand controlpressure from the modulator valve fed through the 3-4 shift valve whendownshifted to a control line 482 to a chamber 483 at one end of valve470. This control pressure holds the control valve element 478 in itsfull left position when it is above a predetermined pressure level andallows it to return to the full right position when it is below thisselected pressure level. When valve 478 is in its left position, driveline pressure from line 184 is connected to an intermediate port 486which is connected to a branch line 488 leading through a check valve498 to a pressure chamber 492 at the end of the 3-4 shift valve element474 so that this valve cannot upshift when this chamber is pressurized.The check valve also connects the branch line 488 to the intermediateline 1 .86. If the shift control valve 470 were in its right-handposition, chamber 492 of the shift valve element 474 is connected to theconverter clutch line 611 through branch line 488 and check valve 490. A3-4 shift could now occur providing a sufficient governor pressuresupplied through line 280 to a pressure chamber 494 which is availableto counteract the force of the spring disposed in chamber 492 urging the3-4 shift valve element 474 to the left. For a 3-4 shift, it isnecessary that the converter clutch line 61 be exhausted signaling thatthe transmission is completely shifted into third gear. it can,therefore, be seen that three requirements must be met before the 3-4shift valve can signal a 3-4 shift when sufficient governor pressure isavailable. They are (l) the solenoid operated valve 484 must bedeenergized, (2) the control pressure in chamber 483 from the modulatorvalve must be below a predetermined pressure, (3) the converterclutchsystem must be exhausted. The intermediate check 498 situatedbetween the control valve element 478 and the shift valve element 474will downshift the transmission out of fourth gear if manualintermediate or manual low range is selected.

The shift valve element 474 has three main functions. In the downshiftposition, as shown, modulator pressure from line 210 which is a functionof engine torque only, is connected to the control line 482. This allows3-4 shifts to only take place at very low engine torques such as wouldoccur during cruising and by backing off on the throttle. In thisdownshift position of valve element 474 drive line 1184 is connected tothe forward clutch line 46 and this pressure holds the. forward clutchengaged and keeps the servo 346 released since the 2-3 shift valveelement 372 is in the upshifted position. The main pressure boost line1172 is connected to port 588 of the 3-4 shift valve when upshifted. Inthe downshifted position the boost line 172 is exhausted through anexhaust 582. When conditionsare such that an upshift occurs, the controlline 482 is connected to the detent port 594 of detent-l line 258. Thiskeeps the control line 482 exhausted unless the detent-l port at thedetent valve 226 becomes pressurized which would move 3-4 control valve479 over to the left and signal a 4-3 downshift. in the upshiftedposition of the shift valve element 474, the forward clutch line 46 isconnected into exhaust 582 which will exhaust the chambers 41 and 42 torelease the forward clutch. The servo control line 352 is exhaustedsince the 2-3 shift valve is in the upshifted position and the servoport 395 is connected to forward clutch port 487. Exhaust 502 is abovethe oil level since the forward clutch 32 is released and rotating infourth gear.

in the upshifted position of the 3-4 valve element 474, the boost port580 and boost line 172 become pressurized with oil from drive line 184.The first land of the shift valve element 474 has a larger diameter thanthe other lands to give it the required amount of shift hysteresis forsubsequent downshifts. The boost line 172 connects to a boost checkvalve 508 where boost pressure fluid is blocked from entry into theintermediate line 186 and is properly routed to the boost plug chamber170 in the main pressure regulator valve system, therefore, boostingline pressure in fourth. The boost check valve 508 controls the boostplug 150 of the main pressure regulator valve system 50 as to boost linepressure in manual intermediate and low gear ranges and also in fourthgear.

There is a converter out restrictor valve 510 in addition to theconverter feed restrictor valve 162. Both of these valves are twoposition systems. Third signal pressure from line 404 is fed to an endchamber 512 to force the valve element 514 to the left against spring516 to block the flow of converter discharge fluid through valve 510forcing the flow through flow control restriction 518 to a cooler 520and a lubricant passage 522. When oil flow through the converter iscontrolled by the restriction 518 bypassing valve 510, the converterfeed restrictor valve 162 opens the converter feed line 118 since thirdsignal pressure pushes the restrictor valve 460 element to theillustrated position.

For automatic drive, the vehicle operator by actuating the manualcontrol, places the manual valve element 180 in the automatic driveposition D. In this position regulated main line pressure is fed throughthe manual valve to the drive line 184. Since governor pressure is lowand torque demand is high for vehicle acceleration from a stationaryposition, all of the shift valve elements will be in their downshiftedposition. Under these conditions the forward clutch line 46 and forwardclutch chambers 41 and 42 are fed with drive line oil through the 34shift valve to effect engagement of the forward clutch 32. With forwardclutch 32 engaged, the sun gear 48 will be driven forwardly. The one-waybrake 90 automatically engages to hold the ring gear for reaction tocondition the transmission for forward low speed operation.

The converter clutch 55 is released in low range since the regulatorvalve element 408 of the 23 accumulator control valve supplies theconverter clutch port 416 and line 61 with regulated converter feedpressure. With regulated pressure fed by line 61 into the converter byway of clutch release chamber 59 clutch 55 is disengaged. There is nofeed of oil to the converter through line 118 and passage 120 at thistime since the converter feed restrictor valve element 460 is blockingfeed line 118 in the absence of third signal pressure in line 404. Fluidexiting from the converter goes through passage 124, the converter outvalve 510 and through the cooler to lubrication passage 522.

As vehicle speed increases and torque demand decreases the l-2 shiftvalve is forced by increasing governor pressure to the upshiftedposition. In this position of the l-2 shift valve element, drive lineoil fed through port 344 is connected to the l-2 clutch line 114. Thisoil is routed to the l-2 accumulator 360 whose piston moves to the leftto increase its volume to calibrate the shift as oil fills intermediatechamber 112 so that piston 110 effects the engagement of intermediatebrake 108. The forward clutch 32 is still engaged since the 3-4 shiftvalve is in the downshift position. With clutch 32 and brake 108 engagedthe gearset will be conditioned for second speed drive. One-way clutch106 is locked and one-way brake is overrunning as previously described.

In second range automatic drive l-2 clutch oil is fed from the upshiftedl-2 shift valve via line 114 into the apply chamber 345 of the servo ofbrake band 103, however, this does not effect brake band apply since therelease chamber 348 is fed with oil from line 352 connected to the RNDline 192 when the 2-3 shift valve is in the downshifted position. As inlow range the converter is fed through the 23 accumulator control valve406 and converter clutch line 61.

As torque demand further decreases and vehicle speed further increases,the 23 shift valve 354 upshifts. 1n the upshifted position of the valveelement 372, pressure from drive line 184 is connected to the thirdsignal port 402 and third signal line 404. The 23 accumulator line 400becomes open to the exhaust 401. When the third signal line ispressurized, the 2-3 accumulator valve shifts in response to thirdsignal pressure in chamber 438 so that converter clutch line 61 isconnected to 23 accumulator line 400 and is exhausted through exhaust401 in the 23 valve. The third signal pressure acts on the end land ofthe converter feed restrictor valve element 460 to shift that valve sothat a converter feed is established in line 118 that is transmitted bypassage 120 into the converter inlet. The converter out restrictor valveelement 514 is shifted so that the converter discharge into passage 124is fed through the restriction 518 into the cooler 520 and then into thelubrication passage 522. With the converter clutch chamber 59 andconverter clutch line 61 open to the exhaust 401 of the 23 shift valveand with the converter being fed through converter feed line 118 theclutch 55 will be engaged by the forces exerted on plate 54 by converterpressure and that of springs 58. With clutch 55 engaged there will bemechanical drive to the ring gear 50 of the rear gear unit.

Since the 3-4 shift valve is still in downshifted position, the forwardclutch line 46 is connected to the drive line to pressure the chambers41 and 42 and maintain the engagement of the forward clutch 32. Withforward clutch 32 applied in addition to the front clutch 55 the gearset38 is driven hydraulically and mechanically to provide a 1:1 splittorque ratio.

Under conditions such as open highway cruising the 3-4 shift may bedesired for high economy operation. This selective shift is madepossible by opening switch 485 so that the solenoid is deenergized toallow the 3-4 shift valve to upshift. The forward clutch apply chambers41 and 42 and line 46 are exhausted through exhaust 502; the forwardclutch 32 disengages. At this time brake band 103 engages drum 94 tohold sun gear 70 for reaction since the servo release chamber 348 isexhausted. This occurs because the 23 shift valve is upshifted and theservo line 352 is connected by the 23 shift valve element with theforward clutch line 46. The upshifted 3-4 shift valve element 474exhausts the servo release oil through the connection of forward clutchline 46 with exhaust 502.

Since the shift valve element 310 of the l-2 shift valve is in theupshifted position as in second and third, drive line oil is connectedto intermediate clutch port 338 and line 114. With servo control chamber348 exhausted, pressure fed by line 1 14 to servo chamber 345 effectsthe engagement of band 103 as well as the intermediate brake 108.

As will be appreciated, this control will provide for automaticdownshifting in response to increasing torque demand and decreasingsignals by the movement of the respective shift valves to theirdownshift positions.

For manual intermediate drive, the manual valve is moved to the Lposition. in this position the manual valve connects pressure from mainline 142 to drive line 184 and intermediate line 186. The low rangedrive line is exhausted through passage 187 and the two exhausts 188.Also, the RND line 192 and reverse line 87 are exhausted being connectedto the exhausts 188. Under these conditions, pressure from intermediateline 186 acts on the end land of 2-3 shift valve element 372 to urge itto the downshifted position and also on boost plug 150 raising minimumline pressure. The servo control chamber 348 is exhausted since servocontrol line 352 is connected by the downshifted 23 shift valve elementto the RND line 192 which is opened at the manual valve to exhaust.Intermediate pressure is effective in chamber 492 of the 3-4 shift valveto urge the 3-4 shift valve element 474 to the downshifted position sothat pressure from drive line 184 is connected to the forward clutchline 46 to effect engagement of forward clutch 32. Drive line oil isconnected to the l-2 clutch line 114 since the l-2 shift valve is in theupshifted position. This effects the engagement of the intermediatebrake 108.

For manual low range, the manual valve is set in the L position so thatregulated pressure is supplied to drive line' 184, intermediate driveline 186 and low range line 182. At vehicle speed below a predeterminedspeed the low control valve element 290 is shiftedby the coil spring toopen the low range port 298 to port 300 of manual low line 302. This oilis fed into the chamber 308 of the l-2 shift valve. The force exerted bythe pressure oil in this chamber moves the ate line 186 is pressurizedin this manual valve position to downshift the 3-4 shift valve element474 by pres- The detent valve element 228 is mechanically connected tothe throttle linkage and is appropriately surizing chamber 492. In thisposition the 3-4 shift valve connects the drive line to forward clutchline 46.

For reverse, the manual valve is moved to the position R to connectreverse line 87 and the RND line 192 y to regulated main line pressure.Reverse oil from line 87 is fed into reverse chamber 86 to effect theengagement of low and reverse brake 78. The l-2 shift valve elements 310and 312 being downshifted will feed reverse line oil from line 87 intoport 326 so that low and reverse chamber 84 will be pressurized toincrease the torque capacity of brake 78. Since reverse clutch line 87is connected with reverse chambers 98 and 99, the reverse clutch 102 isapplied.

Line pressure is boosted to increase the capacity of the engagedfriction devices in reverse. This pressure boost occurs because reverseline pressure is fed into chamber 149 and the modulator trim and reverseboost valve element 148 is forced by reverse pressure into biasingengagement against the main regulator valve element so that it regulatesa higher main line pressure line 142.

moved in direct response to throttle pedal movement to provide for 3-2and 4-3 part throttle downshifts and wide open throttle 3-2 and 2-ldownshifts.

A 32 part throttle downshift can be made below a predetermined vehiclespeed, 50 mph for example. At light throttle the detent valve isreleased and the 3-2 part throttle line 262 is exhausted through exhaustport 264. When an increased torque demand is made, the detent valveelement 228 can be moved to the 3-2 position so that the 3-2.partthrottle line 262 is connected to modulator trim pressure line 218.Pressure fluid is fed through the 3-2 part throttle line 262 to port 380in the 2-3 shift valve. The pressure build-up in the associated pressurechamber forces the 3-2 control valve element 370 and the 2-3 shift valveelement 372 to the downshifted position. In this position the thirdsignal line 404 is exhausted so that the converter feed restrictor valveblocks the supply of fluid to the converter through converter feed line118. However, the converteris supplied with oil through feed line 61since line 118 is connected by the downshifted 2-3 shift valve to the2-3 accumulator line 408. The 2-3 accumulator control valve elementshifts so that converter clutch feed line 61 and feed passage areconnected to converter feed line 118. The supply of pressure fluid intoclutch chamber 59 effects disengagement of clutch 55. The intermediatebrake 188 is applied since the l-2 shift valve element is in the upshiftposition and drive line pressure is connected to the l-2 clutch line184. The forward clutch is applied since the 3-4 shift valve is indownshifted position and drive line oil is fed into forward clutch linethrough line 46. Modulator shift valve oil fed from the detent valvethrough line 258 to the 2-3 shift valve opposes governor pressure sothat the shift schedule is changed.

The 4-3 part throttle downshift can be obtained by moving the detentvalve to the 4-3 or D-] position. In this valve element position, the3-2 part throttle line 262 is connected to port 225 and is fed withmodulator trim pressure. Also, the modulator shift valve line 258 is fedwith modulator trim pressure. The detent-l line 250 is fed a regulatedpressure from the detent regulator valve 254.

The 3-4 shift valve element is in upshifted position and detentregulator oil is fed by the detent-1 line to the chamber 217 of the 3-4shift valve. This oil is then fed intothe control line 482 which leadsto control chamber 483 between the control valve elements 470 and 472.The control valve element 470 is downshifted to connect drive linepressure to the intermediate branch line 488. Drive pressure in chamber492 of the 3-4 shift valve causes this valve to downshift. Theintermediate check ball seats to prevent any flow into line 186.

With the 3-4 shift valve downshifted, drive line oil is again fed to theforward clutch line 46 to apply forward clutch 32. The servo 346 for thebrake band 183 is released by the supply of forward drive oil being fedinto servo control line 352 in the 2-3 shift valve. The 2-3 accumulatorstays upshifted so that converter clutch line 61 is connected to the 2-3accumulator line 408 which is open to exhaust 401 at the 23 shift valve.This exhaust of the converter clutch control chamber 59 allows converterpressure to effect engagement of the front clutch 55 which is engaged inboth direct and overdrive. The intermediate clutch is also engagedthrough the upshifted 1-2 shift valve.

Wide open throttle 4-2, 3-2 and 2-1 downshifts are obtained by placingthe detent valve in the D-2 position. The 3-2 part throttle line 262remains connected to the modulator trim line 218 so that the 2-3 shiftvalve element is urged by the shift control valve 370 to the downshiftedposition. The modulator shift valve line 258 is connected to themodulator trim line 218. The detent-2 line 246 is connected to thedetent regulator pressure fed through line 276; detent regulatedpressure is fed by the detent-2 line to the l-2 and 2-3 shift valves. Inthe upshifted position this pressure is fed to the shift control valveelements 312 and 370 to urge them toward the downshifted position. Ifthe vehicle is cruising in direct drive, a wide open throttle causes a3-2 downshift above a predetermined speed and a 3-1 downshift below thatspeed. If the vehicle were operating in fourth gear, a 4-2 downshiftwould be accomplished.

This invention is not limited to the details of the construction shownand described for purposes of illustrating the invention for othermodifications will occur to those skilled in the art.

What is claimed is:

1. In an automatic shifting transmission having a rotatable input and arotatable output, a hydrodynamic unit operatively connected to saidinput, gearing means operatively connecting said hydrodynamic unit andsaid output, a plurality of hydraulically operated friction driveestablishing devices operatively connected to said gearing means andselectively engageable and disengageable for providing a plurality ofdifferent input- /output speed ratios for the forward drive of avehicle, hydraulic system means for automatically controlling the applyand release of said friction drive establishing devices and theautomatic shifting of said transmission, said hydraulic system meanscomprising: a source of regulated hydraulic pressure, first and secondand third shift valve means each operatively connected to said sourceand to said friction drive establishing devices and being movable toupshift and downshift positions for effecting the engagement anddisengagement of said friction drive establishing devices, first signalmeans operatively connected to said transmission and hydraulicallyconnected to each said shift valve means exerting a force on each saidshift valve means directed toward the upshift position of saidshiftvalve means, second signal means reflecting torque demanded of saidtransmission hydraulically connected to each said shift valve means forexerting a force thereon directed toward the downshift position of eachsaid valve means, said third shift valve means comprising a shiftervalve element movable between upshift and downshift positions andfurther comprising first and second control valve means, said firstcontrol valve means having a shiftable valve element and a hydrauliccontrol chamber therein, biasing means for urging said lastmentionedshiftable valve element toward a first position, fluid passage meanshydraulically connecting said source to said first control valve means,fluid passage means connecting said control chamber to said secondsignal means through said shifter valve element only when said shiftervalve element is in a downshift position to move said shiftable valveelement from said first position so that pressure from said source fedto said first control valve means is directed to said third shift valvemeans to exert a force on said shifter valve element thereof sufficientto hold said shifter valve element in a downshift position until theforce from said second signal means is reduced to a level allowing saidbiasing means to move said shiftable valve element of said first controlvalve to a first position to block the feed of pressure fluid from saidsource to said third shift valve means through said first control valvemeans to thereby allow said first signal means to move said shiftervalve element to an upshift position, and said second control valvemeans having selectively energizable means to move said valve element ofsaid first control valve means to a position to inhibit the upshift ofsaid shifter valve means for all upshift forces exerted on said shiftervalve means by said first signal means.

2. In an automatic shifting transmission having a rotatable input and arotatable output, torque transmitting means including gearing meansoperatively connecting said input and said output, a plurality ofhydraulically operated friction drive establishing devices operativelyconnected to said gearing means and selectively engageable anddisengageable for providing a plurality of different input/output speedratios for forward drive of a vehicle, hydraulic system means forautomatically controlling the apply and release of said friction driveestablishing devices and the automatic shifting of said transmission,said hydraulic system means comprising: a source of pressure regulatedhydraulic fluid, a plurality of shift valve means operatively connectedto said source and to said friction drive establishing devices and beingmovable to upshift and downshift positions for effecting the engagementand disengagement of said friction drive establishing devices, firstsignal means operatively connected to said transmission andhydraulically connected to said shift valve means exerting a forcethereon directed toward the upshift position of said valve means, secondsignal means operatively connected to said transmission andhydraulically connected to said shift valve means exerting a forcethereon directed toward the downshift position of said valve means,control valve means hydraulically connected to one of said shift valvemeans, means hydraulically connecting said last mentioned control valvemeans to said fluid pressure source, said control valve meanshaving acontrol valve element movable between first and second positions,actuator means for urging said control valve element to said firstposition, a control chamber operatively connected to said second signalmeans through said last mentioned shift valve means only when said lastmentioned shift valve means is in a downshift position so that pressurefrom said fluid pressure source is fed to said last mentioned shiftvalve means to inhibit its upshifting by the force exerted by said firstsignal means until the force exerted by said second signal means isreduced to a predetermined force allowing said actuator means to movesaid control valve element to said second position blocking the feed ofpressure to said last mentioned shift valve from said control valve.

3. The transmission defined in claim 2 wherein said hydraulic systemmeans further comprises a second control valve means, means operativelyconnecting said second control valve means with said first control valvemeans so that said second control valve means can shift said firstcontrol valve means, hydraulic passage means-operatively connecting saidsecond control valve means with said source and selectively operableexhaust means operatively connected to said second controi valve meansto selectively exhaust pressure fluid from said second control valvemeans to permit pressure from said source to move said first and secondcontrol valve means together to positions whereby pressure fluid is fedfrom said first control valve means to said last mentioned shift valvemeans to prevent the force exerted by the pressure of said first signalmeans from moving said last mentioned shift valve means to an upshiftedposition.

4. In an automatic shifting transmission having a ro tatable input and arotatable output, torque transmitting means comprising gearing meansoperatively connecting said input and said output, a plurality ofhydraulically operated friction drive establishing devices operativelyconnected to said gearing means and selectively engageable anddisengageable for providing a plurality of different forward driveinput/output speed ratios, hydraulic system means for automaticallycontrolling the apply and release of said friction drive establishingdevices and the automatic shifting of said transmission, said hydraulicsystem means comprising a source of pressurized hydraulic fluid, aplurality of shift valve means operatively connected to said source andto said friction drive establishing devices, said shift valve meanshaving valve elements movable to upshift and downshift positions foreffecting the engagement and disengagement of said friction driveestablishing devices for automatically shifting said gear means betweendifferent'input/output speed ratios, first signal means operativelyconnected to said transmission and hydraulically connected to said shiftvalve means exerting a force thereon directed toward the upshiftposition, second signal means operatively connected to said transmissionand hydraulically connected to said shift valve means exerting a forcethereon directed toward the downshift position, control valvemeans forone of said shift valve means operatively connected to said source offluid pressure, said control valve means having a valve elementshiftable between closed and open positions for controlling the supplyof pressure fluid from said sourceof fluid pressure to said lastmentioned shift valve, and a second control valve means movable toward apredetermined position to selectively contact and move said controlvalve element to said open position to thereby connect said lastmentioned shift valve means with said source of fluid pressure.

5. The transmission defined in claim 4, said second control valve havinga valve element for directly contacting the valve element in said firstcontrol valve'and having a land which forms first and second pressurechambers, means for connecting said source to said first pressurechamber, a flow control orifice formed in said land connecting saidpressure chambers, an exhaust port operatively connected to said secondpressure chamber, and closure means to selectively open said exhaustport to permit a buildup in pressure in said first chamber so that saidvalve element of said second control valve moves to position the firstcontrol valve so that pressure from said source means is fed to saidlast mentioned shift valve means to hold said last mentioned shift valvemeans in a downshift position.

6. in a control for a transmission having a transmission input and anoutput operatively connected by torque transmitting means including agear unit selectively conditioned by a plurality of hydraulicallyoperated friction drive establishing devices for a plurality ofdifferent input/output speed ratios comprising a source of pressurizedfluid, shift valve means operatively connected to said source and tosaidfriction drive establishing devices, first and second signal meansoperatively connected to said shift valve means, said shift valve meanshaving valve element means movable by the opposing of said signal meansbetween upshift and downshift positions for controlling the engagementand disengagement of said friction drive establishing devices, controlvalve means for one of said shift valve means operatively connected tosaid source, a detent valve having a valve element movable to aplurality of positions in accordance with a torque demand signal, saidvalve element being movable to a predetermined position in which apressure supplied to said detent valve is routed to said control valvemeans through said last mentioned shift valve means when in theupshifted position, said control valve having a valve element shiftablein response to the pressure supplied to said control valve from saiddetent valve to a position opening said source to said shift valve meansto cause said shift valve element in said last mentioned shift valvemeans to move to the downshift position.

7. In a control for a transmission having a transmission input and anoutput operatively connected by a hydrodynamic unit and by a gear unitselectively conditioned by a plurality of hydraulically operatedfriction drive establishing devices for a plurality of differentinput/output speed ratios comprising a source of pressurized fluid,shift valve means operatively connected to said source and to saidfriction drive establishing devices, first and second signal meansoperatively connected to said shift valve means, said shift valve meanshaving valve element means movable by opposing forces of said signalmeans on said valve element between upshift and downshift positions forcontrolling the engagement and disengagement of said friction driveestablishing devices, control valve means for one of said shift valvemeans operatively connected to said source, a detent valve having avalve element movable to a plurality of positions for forcing saidtransmission to downshift, said detent valve element being movable toone of said positions inwhich a pressure supplied to said detent valvefrom said source is routed to said control valve means through said lastrecited shift valve means when in the upshifted position, said controlvalve having a valve element shiftable in response to the pressuresupplied thereto from said detent valve to a position opening saidsource to said last recited shift valve means so that said last recitedshift valve means moves to the downshift position.

d. The control defined in claim 7, said shift valve means comprising:first, second and third shift valves for controlling 1-2, 2-3 and 3-4gear unit speed ratio changes respectively, additional control valvemeans operatively connected to first and second shift valverespectively, and hydraulic passage means directly connecting saiddetent valve means to said additional control valve means to provide for3-2, 31 and 4-2 forced downshifts on the positioning of said detentvalve element to other of said positions.

9. In a control for a transmission having a transmission input and atransmission output, a multi-speed gear unit operatively connecting saidinput to said output, providing at least four forward drive input/outputspeed ratios, a plurality of hydraulically operated and selectivelyengageable friction drive establishing devices operatively connected tosaid gear unit for chang ing the speed of said transmission output, saidcontrol comprising a source of pressurized fluid; 1-2, 2-3 and 3-4 shiftvalves operatively connected to said source and to said friction driveestablishing devices for controlling the engagement thereof, firstsignal means providing a hydraulic force proportional to the speed ofsaid transmission output for urging each of said shift valve means to anupshift position, second signal means providing a force proportional totorque demand from said transmission for urging each of said shift valvemeans to a downshift position, a detent valve operatively connected tosaid source of fluid pressure and to each of said shift valves, saiddetent valve having a shiftable valve element movable to a firstposition to force the 23 shift valve to downshift when said first signalmeans would normally force said 23 shift valve to an upshift positionand movable to a second position to force a 4-3 downshift and movable toa third position to force said 4-3 and said 3-2 shift valves todownshift for a four to two speed ratio shift.

10. A control for automatically shifting a multi speed transmissionhaving a transmission input and an output operatively connected to atorque converter and a selectively engageable clutch connected inparallel for selectively driving a gear unit conditioned by a pluralityof hydraulically operated friction drive establishing devices forforward low, intermediate, direct, and overdrive input/output speedratios and for a reverse drive ratio comprising; a source of pressurizedfluid, first, second and third shift valve means operatively connectedto said source and to said friction drive establishing devices, governorvalve means and modulator valve means providing a first and secondsignal means operatively connected to said shift valve means forupshifting and downshifting said gear unit, selector valve means forselectively conditioning said transmission for low, intermediate,automatic change-speed forward drive and reverse drive, a control valveoperatively connected to said source and to one of said shift valves forcontrolling the clutch parallel to. the torque converter, said lastmentioned shift valve having valve element means movable by signals fromsaid governor and modulator valve means to actuate said clutch controlvalve means to effect the disengagement of the clutch for all converterlow and intermediate drives and effect the engagement of the clutch formechanical drive of the gear unit for direct and overdrive operation.

11. A hydraulic control for a geared change-speed transmissioncomprising a source of fluid pressure, shift valve means for changingthe speed ratio of said transmission, means hydraulically connectingsaid shift valve means to said source of fluid pressure and to saidtransmission, said shift valve means having a valve ele ment movablebetween upshift and downshift positions, control valve meanshydraulically connected to said source of fluid pressure, first fluidpassage means hydraulically connecting said control valve means to saidshift valve means, a detent valve, means hydraulically connecting saiddetent valve to said source, second fluid passage means hydraulicallyconnecting said detent valve to said shift valve means, third fluidpassage means hydraulically connecting said shift valve means to saidcontrol valve means, said detent valve having a valve element movable toa position whereby fluid pressure from said source is fed through saiddetent valve and said second passage means into said shift valve onlywhen said valve element of said shift valve means is in an upshiftposition and through said third fluid passage means into said controlvalve means to thereby shift said control valve means to a predeterminedposition in which pressure fluid from said source is fed through saidcontrol valve means and said first fluid passage means to said shiftvalve means to move said shift valve element to a downshift position tothereby downshift said transmission.

12. The control designed in claim 11 wherein said control valve meanscomprises first and second shiftable control valve elements, meansoperatively connecting said first and second control valve elements sothat said first control valve element can shift said second controlvalve element, said control valve means having a first chamber formed onone side of said first control valve element, means operativelyconnecting said first fluid chamber with said source of fluid pressure,a second control chamber formed on the other side of said first controlvalve element, fluid flow control means interconnecting said first andsecond cham bers, exhaust valve means for exhausting fluid from saidsecond control chamber so that pressure from said source acting on saidfirst control valve element will urge said control valve elements to aposition whereby pressure from said source fed through said second con-'trol valve to said shift valve downshifts said transmission, and meansfor closing said exhaust valve means whereby pressure in said secondcontrol chamber moves said first control valve element from said secondcontrol valve element so that said second control valve element can beshifted to effect the upshift of said shift valve element and saidtransmission.

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1. In an automatic shifting transmission having a rotatable input and arotatable output, a hydrodynamic unit operatively connected to saidinput, gearing means operatively connecting said hydrodynamic unit andsaid output, a plurality of hydraulically operated friction driveestablishing devices operatively connected to said gearing means andselectively engageable and disengageable for providing a plurality ofdifferent input/output speed ratios for the forward drive of a vehicle,hydraulic system means for automatically controlling the apply andrelease of said friction drive establishing devices and the automaticshifting of said transmission, said hydraulic system means comprising: asource of regulated hydraulic pressure, first and second and third shiftvalve means each operatively connected to said source and to saidfriction drive establishing devices and being movable to upshift anddownshift positions for effecting the engagement and disengagement ofsaid friction drive establishing devices, first signal means operativelyconnected to said transmission and hydraulically connected to each saidshift valve means exerting a forCe on each said shift valve meansdirected toward the upshift position of said shift valve means, secondsignal means reflecting torque demanded of said transmissionhydraulically connected to each said shift valve means for exerting aforce thereon directed toward the downshift position of each said valvemeans, said third shift valve means comprising a shifter valve elementmovable between upshift and downshift positions and further comprisingfirst and second control valve means, said first control valve meanshaving a shiftable valve element and a hydraulic control chambertherein, biasing means for urging said last-mentioned shiftable valveelement toward a first position, fluid passage means hydraulicallyconnecting said source to said first control valve means, fluid passagemeans connecting said control chamber to said second signal meansthrough said shifter valve element only when said shifter valve elementis in a downshift position to move said shiftable valve element fromsaid first position so that pressure from said source fed to said firstcontrol valve means is directed to said third shift valve means to exerta force on said shifter valve element thereof sufficient to hold saidshifter valve element in a downshift position until the force from saidsecond signal means is reduced to a level allowing said biasing means tomove said shiftable valve element of said first control valve to a firstposition to block the feed of pressure fluid from said source to saidthird shift valve means through said first control valve means tothereby allow said first signal means to move said shifter valve elementto an upshift position, and said second control valve means havingselectively energizable means to move said valve element of said firstcontrol valve means to a position to inhibit the upshift of said shiftervalve means for all upshift forces exerted on said shifter valve meansby said first signal means.
 2. In an automatic shifting transmissionhaving a rotatable input and a rotatable output, torque transmittingmeans including gearing means operatively connecting said input and saidoutput, a plurality of hydraulically operated friction driveestablishing devices operatively connected to said gearing means andselectively engageable and disengageable for providing a plurality ofdifferent input/output speed ratios for forward drive of a vehicle,hydraulic system means for automatically controlling the apply andrelease of said friction drive establishing devices and the automaticshifting of said transmission, said hydraulic system means comprising: asource of pressure regulated hydraulic fluid, a plurality of shift valvemeans operatively connected to said source and to said friction driveestablishing devices and being movable to upshift and downshiftpositions for effecting the engagement and disengagement of saidfriction drive establishing devices, first signal means operativelyconnected to said transmission and hydraulically connected to said shiftvalve means exerting a force thereon directed toward the upshiftposition of said valve means, second signal means operatively connectedto said transmission and hydraulically connected to said shift valvemeans exerting a force thereon directed toward the downshift position ofsaid valve means, control valve means hydraulically connected to one ofsaid shift valve means, means hydraulically connecting said lastmentioned control valve means to said fluid pressure source, saidcontrol valve means having a control valve element movable between firstand second positions, actuator means for urging said control valveelement to said first position, a control chamber operatively connectedto said second signal means through said last mentioned shift valvemeans only when said last mentioned shift valve means is in a downshiftposition so that pressure from said fluid pressure source is fed to saidlast mentioned shift valve means to inhibit its upshifting by the forceexerted by said first signal means until the forCe exerted by saidsecond signal means is reduced to a predetermined force allowing saidactuator means to move said control valve element to said secondposition blocking the feed of pressure to said last mentioned shiftvalve from said control valve.
 3. The transmission defined in claim 2wherein said hydraulic system means further comprises a second controlvalve means, means operatively connecting said second control valvemeans with said first control valve means so that said second controlvalve means can shift said first control valve means, hydraulic passagemeans operatively connecting said second control valve means with saidsource and selectively operable exhaust means operatively connected tosaid second control valve means to selectively exhaust pressure fluidfrom said second control valve means to permit pressure from said sourceto move said first and second control valve means together to positionswhereby pressure fluid is fed from said first control valve means tosaid last mentioned shift valve means to prevent the force exerted bythe pressure of said first signal means from moving said last mentionedshift valve means to an upshifted position.
 4. In an automatic shiftingtransmission having a rotatable input and a rotatable output, torquetransmitting means comprising gearing means operatively connecting saidinput and said output, a plurality of hydraulically operated frictiondrive establishing devices operatively connected to said gearing meansand selectively engageable and disengageable for providing a pluralityof different forward drive input/output speed ratios, hydraulic systemmeans for automatically controlling the apply and release of saidfriction drive establishing devices and the automatic shifting of saidtransmission, said hydraulic system means comprising a source ofpressurized hydraulic fluid, a plurality of shift valve meansoperatively connected to said source and to said friction driveestablishing devices, said shift valve means having valve elementsmovable to upshift and downshift positions for effecting the engagementand disengagement of said friction drive establishing devices forautomatically shifting said gear means between different input/outputspeed ratios, first signal means operatively connected to saidtransmission and hydraulically connected to said shift valve meansexerting a force thereon directed toward the upshift position, secondsignal means operatively connected to said transmission andhydraulically connected to said shift valve means exerting a forcethereon directed toward the downshift position, control valve means forone of said shift valve means operatively connected to said source offluid pressure, said control valve means having a valve elementshiftable between closed and open positions for controlling the supplyof pressure fluid from said source of fluid pressure to said lastmentioned shift valve, and a second control valve means movable toward apredetermined position to selectively contact and move said controlvalve element to said open position to thereby connect said lastmentioned shift valve means with said source of fluid pressure.
 5. Thetransmission defined in claim 4, said second control valve having avalve element for directly contacting the valve element in said firstcontrol valve and having a land which forms first and second pressurechambers, means for connecting said source to said first pressurechamber, a flow control orifice formed in said land connecting saidpressure chambers, an exhaust port operatively connected to said secondpressure chamber, and closure means to selectively open said exhaustport to permit a buildup in pressure in said first chamber so that saidvalve element of said second control valve moves to position the firstcontrol valve so that pressure from said source means is fed to saidlast mentioned shift valve means to hold said last mentioned shift valvemeans in a downshift position.
 6. In a control for a transmission havinga Transmission input and an output operatively connected by torquetransmitting means including a gear unit selectively conditioned by aplurality of hydraulically operated friction drive establishing devicesfor a plurality of different input/output speed ratios comprising asource of pressurized fluid, shift valve means operatively connected tosaid source and to said friction drive establishing devices, first andsecond signal means operatively connected to said shift valve means,said shift valve means having valve element means movable by theopposing of said signal means between upshift and downshift positionsfor controlling the engagement and disengagement of said friction driveestablishing devices, control valve means for one of said shift valvemeans operatively connected to said source, a detent valve having avalve element movable to a plurality of positions in accordance with atorque demand signal, said valve element being movable to apredetermined position in which a pressure supplied to said detent valveis routed to said control valve means through said last mentioned shiftvalve means when in the upshifted position, said control valve having avalve element shiftable in response to the pressure supplied to saidcontrol valve from said detent valve to a position opening said sourceto said shift valve means to cause said shift valve element in said lastmentioned shift valve means to move to the downshift position.
 7. In acontrol for a transmission having a transmission input and an outputoperatively connected by a hydrodynamic unit and by a gear unitselectively conditioned by a plurality of hydraulically operatedfriction drive establishing devices for a plurality of differentinput/output speed ratios comprising a source of pressurized fluid,shift valve means operatively connected to said source and to saidfriction drive establishing devices, first and second signal meansoperatively connected to said shift valve means, said shift valve meanshaving valve element means movable by opposing forces of said signalmeans on said valve element between upshift and downshift positions forcontrolling the engagement and disengagement of said friction driveestablishing devices, control valve means for one of said shift valvemeans operatively connected to said source, a detent valve having avalve element movable to a plurality of positions for forcing saidtransmission to downshift, said detent valve element being movable toone of said positions in which a pressure supplied to said detent valvefrom said source is routed to said control valve means through said lastrecited shift valve means when in the upshifted position, said controlvalve having a valve element shiftable in response to the pressuresupplied thereto from said detent valve to a position opening saidsource to said last recited shift valve means so that said last recitedshift valve means moves to the downshift position.
 8. The controldefined in claim 7, said shift valve means comprising: first, second andthird shift valves for controlling 1-2, 2-3 and 3-4 gear unit speedratio changes respectively, additional control valve means operativelyconnected to first and second shift valve respectively, and hydraulicpassage means directly connecting said detent valve means to saidadditional control valve means to provide for 3-2, 3-1 and 4-2 forceddownshifts on the positioning of said detent valve element to other ofsaid positions.
 9. In a control for a transmission having a transmissioninput and a transmission output, a multi-speed gear unit operativelyconnecting said input to said output, providing at least four forwarddrive input/output speed ratios, a plurality of hydraulically operatedand selectively engageable friction drive establishing devicesoperatively connected to said gear unit for changing the speed of saidtransmission output, said control comprising a source of pressurizedfluid; 1-2, 2-3 and 3-4 shift valves operatively connected to saidsource and to said friction drive establishing devices for controllingthe engagement thereof, first signal means providing a hydraulic forceproportional to the speed of said transmission output for urging each ofsaid shift valve means to an upshift position, second signal meansproviding a force proportional to torque demand from said transmissionfor urging each of said shift valve means to a downshift position, adetent valve operatively connected to said source of fluid pressure andto each of said shift valves, said detent valve having a shiftable valveelement movable to a first position to force the 2-3 shift valve todownshift when said first signal means would normally force said 2-3shift valve to an upshift position and movable to a second position toforce a 4-3 downshift and movable to a third position to force said 4-3and said 3-2 shift valves to downshift for a four to two speed ratioshift.
 10. A control for automatically shifting a multi speedtransmission having a transmission input and an output operativelyconnected to a torque converter and a selectively engageable clutchconnected in parallel for selectively driving a gear unit conditioned bya plurality of hydraulically operated friction drive establishingdevices for forward low, intermediate, direct, and overdriveinput/output speed ratios and for a reverse drive ratio comprising; asource of pressurized fluid, first, second and third shift valve meansoperatively connected to said source and to said friction driveestablishing devices, governor valve means and modulator valve meansproviding a first and second signal means operatively connected to saidshift valve means for upshifting and downshifting said gear unit,selector valve means for selectively conditioning said transmission forlow, intermediate, automatic change-speed forward drive and reversedrive, a control valve operatively connected to said source and to oneof said shift valves for controlling the clutch parallel to the torqueconverter, said last mentioned shift valve having valve element meansmovable by signals from said governor and modulator valve means toactuate said clutch control valve means to effect the disengagement ofthe clutch for all converter low and intermediate drives and effect theengagement of the clutch for mechanical drive of the gear unit fordirect and overdrive operation.
 11. A hydraulic control for a gearedchange-speed transmission comprising a source of fluid pressure, shiftvalve means for changing the speed ratio of said transmission, meanshydraulically connecting said shift valve means to said source of fluidpressure and to said transmission, said shift valve means having a valveelement movable between upshift and downshift positions, control valvemeans hydraulically connected to said source of fluid pressure, firstfluid passage means hydraulically connecting said control valve means tosaid shift valve means, a detent valve, means hydraulically connectingsaid detent valve to said source, second fluid passage meanshydraulically connecting said detent valve to said shift valve means,third fluid passage means hydraulically connecting said shift valvemeans to said control valve means, said detent valve having a valveelement movable to a position whereby fluid pressure from said source isfed through said detent valve and said second passage means into saidshift valve only when said valve element of said shift valve means is inan upshift position and through said third fluid passage means into saidcontrol valve means to thereby shift said control valve means to apredetermined position in which pressure fluid from said source is fedthrough said control valve means and said first fluid passage means tosaid shift valve means to move said shift valve element to a downshiftposition to thereby downshift said transmission.
 12. The controldesigned in claim 11 wherein said control valve means comprises firstand seconD shiftable control valve elements, means operativelyconnecting said first and second control valve elements so that saidfirst control valve element can shift said second control valve element,said control valve means having a first chamber formed on one side ofsaid first control valve element, means operatively connecting saidfirst fluid chamber with said source of fluid pressure, a second controlchamber formed on the other side of said first control valve element,fluid flow control means interconnecting said first and second chambers,exhaust valve means for exhausting fluid from said second controlchamber so that pressure from said source acting on said first controlvalve element will urge said control valve elements to a positionwhereby pressure from said source fed through said second control valveto said shift valve downshifts said transmission, and means for closingsaid exhaust valve means whereby pressure in said second control chambermoves said first control valve element from said second control valveelement so that said second control valve element can be shifted toeffect the upshift of said shift valve element and said transmission.